Oxidation catalyst for cleaning exhaust gas

Abstract

An oxidation catalyst for cleaning exhaust gas, excellent in the function of oxidizing high boiling point materials such as particulates and polycyclic aromatic hydrocarbons contained in the exhaust gas of internal-combustion engines is provided. The catalyst is a composite oxide containing two kinds of metal elements, wherein, when the two kinds of metal elements are defined as A and B, the value of the ionic radius of metal element A/the ionic radius of metal element B is in the range of from 1.349 to 1.580. The metal element A is selected from the group consisting of Sc, Y, Ho, Er, Tm, Yb, and Lu, and the metal element B is Mn. The composite oxide has a hexagonal structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a set of X-ray diffraction patterns showing the structures of composite oxides forming oxidation catalysts for cleaning exhaust gas according to the present invention; and

FIG. 2 is a bar graph showing the relationship between the value of the ionic radius ratio of each composite oxide and the combustion peak temperature of carbon black in each oxidation catalyst for cleaning exhaust gas according to the present invention.

Claims

1. An oxidation catalyst for cleaning exhaust gas comprising a composite oxide containing two kinds of metal elements and, when the two kinds of metal elements are defined as A and B, represented by the general formula of ABO3, wherein the value of (the ionic radius of metal element A)/(the ionic radius of metal element B) is in the range of from 1.349 to 1.580.

2. The oxidation catalyst for cleaning exhaust gas according to claim 1, wherein said metal element A is selected from the group consisting of Sc, Y, Ho, Er, Tm, Yb, and Lu, and said metal element B is Mn.

3. The oxidation catalyst for cleaning exhaust gas according to claim 1, wherein said composite oxide has a hexagonal structure.